Heat exchanger

ABSTRACT

A heat exchanger, in which flowing medium flows, includes a first tank, a second tank, a core part and a flow accelerating means. The first tank is provided with an inlet port, the second tank being disposed apart from the first tank. The core part has a plurality of tubes and a plurality of fins. The tubes have both end portions being fluidically connected with the first tank and the second tank, respectively. Each of the fins is arranged between the adjacent tubes. The flow accelerating mean is provided inside the first tank so as to accelerate a flow speed of the flowing medium, which enters an inner space of the first tank through the inlet port, in the first tank in a longitudinal direction of the first tank.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat exchanger using cooling flowingmedium that runs through tubes fluidically connected between tanks.

2. Description of the Related Art

A conventional heat exchanger is disclosed in Japanese PatentApplication laid-open publication No. 2007-107799. This conventionalheat exchanger includes a pair of long tanks, a plurality of tubes and aplurality of fins. The tanks are arranged apart from each other in avertical direction, where an upper one of them is provided with an inletport and a lower one thereof is provided with an outlet port. The tubesare disposed between the tanks, both end portions of the tubes beinginserted into and fixed to the tanks, respectively. This enables flowingmedium, such as coolant, to flow into the upper tank through the inletport and then flow to the lower tank through the tubes, finally beingdischarged through the outlet port from the lower tank. The fins arearranged between the adjacent tubes so as to cool the flowing mediumwhile it passes through the tubes.

The above known conventional heat exchanger, however, encounters aproblem in that durability of the heat exchanger is deteriorated due tothermal stress caused because of the following reasons.

In the conventional heat exchanger, when a high-temperature flowingmedium enters the upper tank, corresponding to an upstream side tank,through the inlet port, a low-temperature flowing medium existing nearthe inlet port is swiftly pushed out toward the lower tank,corresponding to a downstream side tank, while the low temperatureflowing medium existing at a portion of the heat exchanger that is faraway from the inlet port cannot be swiftly pushed out toward the lowertank. It takes a long time for the high-temperature flowing medium toreach the far-away portion and replace the low-temperature flowingmedium existing there.

In this state, the low-temperature flowing medium near the inlet port ismoved toward the lower tank, being heated up due to direct mixture withthe high-temperature flowing medium, while the low-temperature flowingmedium at the portion that is wide apart from the inlet port is alsopushed to move toward the lower tank without being heated up due to themixture with the high-temperature flowing medium.

It causes a significant variation in temperature distribution of theflowing medium existing in the upstream side tank so that the variationbecomes larger as the high-temperature flowing medium repeats flowing inand out from the heat exchanger. It further causes a notable temperaturedifference among the tubes according to their locations. Consequently,different thermal expansions thereof are generated among the tubes todeteriorate the durability of the heat exchanger.

It is, therefore, an object of the present invention to provide a heatexchanger which overcomes the foregoing drawbacks and can decreasethermal stress differences of a tank and a core part, thereby improvingdurability of the heat exchanger.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided a heatexchanger, in which flowing medium flows, including a first tank, asecond tank, a core part and a flow accelerating means. The first tankis provided with an inlet port, and the second tank is disposed apartfrom the first tank. The core part has a plurality of tubes and aplurality of fins, the tubes having both end portions being fluidicallyconnected with the first tank and the second tank, respectively, andeach of the fins being arranged between the adjacent tubes. The flowaccelerating mean is provided inside the first tank so as to acceleratea flow speed of the flowing medium, which enters an inner space of thefirst tank through the inlet port, in the first tank in a longitudinaldirection of the first tank.

Therefore, the heat exchanger of the present invention can decreasethermal stress differences of a tank and a core part, thereby improvingdurability of the heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention willbecome apparent as the description proceeds when taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a rear view showing a radiator as a heat exchanger of a firstembodiment according to the present invention;

FIG. 2 is a rear view showing a core part of the radiator of the firstembodiment shown in FIG. 1;

FIG. 3 is an enlarged cross sectional view showing an inlet port and itsperipheral parts of the radiator of the first embodiment, taken along aline S3-S3 in FIG. 1;

FIG. 4 is an enlarged cross sectional view showing a tank with a firstrib portion of the radiator of the first embodiment, taken along a lineS4-S4 in FIG. 1;

FIG. 5 is a cross sectional side view showing the tank shown in FIG. 1;

FIG. 6 is a perspective view showing the tank shown in FIG. 1;

FIG. 7 is a cross sectional side view showing a tank of a heat exchangerof a second embodiment according to the present invention;

FIG. 8 is a perspective view showing the tank shown in FIG. 7;

FIG. 9 is a perspective view showing a tank of a heat exchanger of athird embodiment according to the present invention;

FIG. 10 is a cross sectional side view showing a tank of a heatexchanger of a fourth embodiment according to the present invention;

FIG. 11 is a perspective view of the tank shown in FIG. 10;

FIG. 12 is a table showing experimental results of the radiator of thefirst embodiment of the present invention;

FIG. 13 is an enlarged cross sectional view showing a tank of amodification according to the present invention;

FIG. 14 is an enlarged cross sectional view showing a tank of anothermodification according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Throughout the following detailed description, similar referencecharacters and numbers refer to similar elements in all figures of thedrawings, and their descriptions are omitted for eliminatingduplication.

In the accompany drawings, “FR” indicates a front side direction of amotor vehicle, and “RR” indicates a rear side direction thereof.

Referring to FIG. 1 and FIG. 2, there is shown a first preferredembodiment of a heat exchanger according to the present invention. Theheat exchanger is a radiator 1 in this embodiment, and the radiator 1 isinstalled on a not-shown front end portion of a vehicle body of a motorvehicle, such as an automobile, in this embodiment.

The radiator 1 has a pair of long tanks 2 and 3 and a core part 4.

The right tank 2 and the left tank 3 are apart from each other in alateral direction of the vehicle body and are made of plastic material.The right tank 2 corresponds to a first tank of the present invention,and the left tank 3 corresponds to a second tank of the presentinvention. Their detail construction will be later described.

The core part 4 is disposed between the right tank 2 and the right tank3, being made of aluminum. The core part 4 includes a right tube plate5, a left tube plate 6, a plurality of flat tubes 7, a pair ofcorrugated fins 8 and a pair of reinforcements 9 and 10.

The right and left tube plates 5 and 6 extend vertically and are formedwith a plurality of holes for respectively receiving both end portionsof the tubes 7. The both end portions of the tubes 7 extend in thelateral direction to be inserted into the holes and are fixed to theright and left tube plates 5 and 6, respectively. Each of the corrugatefins 8 is arranged between the adjacent tubes 7, extending in thelateral direction. Both end portions of the upper reinforcement 9 andthe lower reinforcement 10 are inserted into and fixed to the right andleft tube plates 5 and 6 at a top portion of the core part 4 and abottom portion thereof, respectively.

At least one side portions of connecting portions that are temporallyassembled are provided with a clad layer of brazing material, or abrazing sheet. This temporally assembled core part 4 is heat-treated ina heating furnace to be integrally formed.

As shown in FIG. 3 and FIG. 4, the right and left tanks 2 and 3 arefixed to the heat-treated core part 4 by means of a plurality of clawportions 11 formed on the right and left tube plates 5 and 6.Specifically, the claw portions 11 are caulked to outer circumferentialportions of the right and left tanks 2 and 3, respectively, with a sealmember placed therebetween at the outer circumferential portions so thatinner spaces of the tanks 2 and 3 can be tightly sealed.

The right tank 2 is formed like a vessel, which is formed with anopening at its core part side. The right tank 2 is provided with aninlet port 13 of the flowing medium on its upper and rear side surface,further being provided with a drain port 14 on its bottom surface. Onthe other hand, the left tank 3 is also formed like a vessel, which isformed with an opening at its core part side and is provided with anoutlet port 15 of the flowing medium on its lower and rear side surface.

In this embodiment, a not-shown inlet pipe and a not-shown outlet pipeare inserted into and fixed to the inlet port 13 and the outlet port 15,respectively. The pipes may be formed with the tanks 2 and 3 as oneunit.

As shown in FIG. 5 and FIG. 6, upper and lower attachment brackets 16are formed on front side surfaces of the tanks 2 and 3, being apart fromeach other I the vertical direction, so that they can fix and support anot-shown condenser on the radiator 1. Further, the tanks 2 and 3 areformed a with a mounting pin 17 on each top surface thereof forsupporting the radiator 1 together with the condenser on a not-shownradiator core support and the like as a part of the vehicle body.

As shown in FIG. 3 to FIG. 6, in the inner space of the right tank 2, afirst rib portion 18 is formed like a plate that projects by apredetermined height H1, as shown in FIG. 4, from its bottom innersurface toward the tube 7, forming a clearance with a length H2 in alateral direction of the tank 2 between a tip portion of the first ribportion 18 and the end portion of the tubes 7. The first rib portion 18extends in the lateral direction of the tank 2 and in the verticaldirection thereof, namely along a longitudinal direction of the righttank 2, being made of plastic material as one unit with the right tank2. The first rib portion 18 corresponds to a first wall portion of thepresent invention.

The first rib portion 18 is bent toward the inlet port 13 in thevicinity thereof the inlet as shown in FIG. 5 and FIG. 6, and its upperbent portion is continuously connected with an upper side of the inletport 13 and its lower bent portion is continuously connected with alower side of the inlet port 13. This divides the inner space of theright tank 2 into a front side passage 19 and two rear side passages 20and 21. Namely, a flow area of the front side passage 19 is set to benarrower than that of the inlet port 13, and the front side passage 19is directly connected with the inlet port 13, extending along thelongitudinal direction of the right tank 2. The upper rear side passage20 and the lower rear side passage 21 are prevented from being directlyconnected with the inlet port 13. The first rib portion 18 correspondsto a flow accelerating means of the present invention. The front sidepassage 19 corresponds to a first passage of the present invention, andthe rear side passages 20 and 21 correspond to a second passage of thepresent invention.

The left tank 3 is constructed similarly to the right tank 2 except thatit has no first rib portion and no drain port and that the outlet port15, instead of the inlet port 13 of the right tank 2, is provided at thelower rear surface of the left tank 3. Accordingly, a description of itsconstruction is omitted herein.

Thus constructed radiator 1 is fixed and supported on the radiator coresupport by using the mounting pins 17, together with the condenser fixedand supported on the front side of the radiator 1 by using theattachment brackets 16.

Then, the pipe is inserted into and fixed to the inlet port 13, and thenit is connected with a not-shown connecting pipe so that the flowingmedium can flow therethrough after the medium cools an object to becooled, such as an engine or an inverter circuit of an electric motor.On the other hand, the other pipe is inserted into and fixed to theoutlet port 15, and then it is connected with a not-shown connectingpipe so that the flowing medium can flow therethrough before the mediumcools the object.

The operation and effects of the radiator 1 of the first embodiment willbe described.

The high-temperature flowing medium, which enters the right tank 2through the inlet port 13, is cooled down due to heat exchanger betweenthe flowing medium and an air flow generated by the motor vehiclerunning (and/or an air flow generated by a motor fan), while it flows tothe left tank 3 through the tubes 7 of the core part 4. Thelow-temperature flowing medium in the left tank 3 is discharged throughthe outlet port 10 to be supplied to the object. The flowing mediumcooled down the object, and then returns to the inlet port 13 of theradiator 1 to circulate in this cooling circuit.

In this operation, after the high-temperature flowing medium enters theinner space of the right tank 2 through the inlet port 13, its flowspeed is accelerated, because it is guided by the rim portion 18 to flowthrough the front side passage 19, of the right tank 2, that the firstrib portion 18 narrows, as indicated by a dashed line M in FIG. 5. Thishigh-temperature flowing medium reaches the top and bottom portions ofthe front side passage 19 in a short time, being mixed up with thelow-temperature flowing medium existing at and near the top and bottomportions. This swiftly mixed-up flowing medium is pushed out from theright tank 2 to the left tank 3 through the tubes 7.

On the other hand, the low-temperature flowing medium in the rear sidepassages 20 and 21 of the right tank 2 is mixed up with thehigh-temperature flowing medium existing in the front side passage 19through the clearance, having the length H2, between the first ribportion 18 and the tubes 7. This mix-up increases the temperature of thelow-temperature flowing medium, decreasing the temperature of thehigh-temperature flowing medium, in the right tank 2.

In other words, the first rib portion 18 guides the high-temperatureflowing medium so as to preferentially flow it through the narrow frontside passage 19, which can shorten the amount of time for thehigh-temperature flowing medium to reach the top and bottom portions,being far away from the inlet port 13, of the right tank 2. In addition,replacement between the high-temperature flowing medium and thelow-temperature flowing medium can be swiftly carried out in the righttank 2, so that the temperature inside of the right tank 2 can beapproximately uniform at any position in a short time.

In addition, it shortens the amount of time for the flowing medium toflow through all the tube 7 at approximately uniform temperature, atemperature distribution of the core part 4 can be approximately uniformin a short time. Therefore, thermal stress due to considerable variationin the temperature distribution of the right tank 2 and the core part 4can be decreased, which can improve the durability of the radiator 1.

Further, the front side passage 19 is provided at a wall portion sideopposite to a wall portion formed with the inlet port 13, which candecrease flow resistance of the flowing medium immediately after itenters the right tank 2 through the inlet port 13 compared to that in acase where the front side passage 19 is provided at the wall portionside formed with the inlet port 13.

Further, the first rib portion 18 and the right tank 2 can be formed asone unit easily and at a low manufacturing cost compared to those thatare independently formed and then are integrally connected with eachother.

The first rib portion 18 can decrease thermal stress generated atconnecting portions of the tubes 7 and the tube plate 5, on which thethermal stress notably acts, in the right tank 2, namely the upstreamside tank, temperature variation of which becomes larger than that ofthe left tank 3, namely the downstream side tank.

Next, a second embodiment of the present invention will be described. Asshown in FIG. 7 and FIG. 8, in a radiator of the second embodiment, afirst rib portion 18 is provided inside a right tank 2 similarly to thefirst embodiment, but a plurality of second rib portions 30 are addedbetween the first rib portion 18 and a wall portion formed with an inletport 13 of the right tank 2, extending in a direction perpendicular to alongitudinal direction of the right tank 2. The second rib portions 30are made of plastic material as one unit with the right tank 2 and thefirst rib portion 18, having the same heights as those of the first ribportion 18. The second rib portions correspond to a second wall portionof the present invention.

Incidentally, the first rib portion 18 has a plurality of injectionportions 38, which are formed like a circular cylinder at not-showngates by curing of molten plastic manual injected therethrough. Theseinjection portions 38 are not indispensable.

These first and second rib portions 18 and 30 divided an inner space ofthe right tank 2 into a front side passage 19 at a wall portion sideopposite to the wall portion formed with the inlet port 30 and aplurality of chambers consisting of two upper chambers 31 and 32 andfive lower chambers 33 to 37. The chambers 31 to 37 have clearances forfluidically communicating with the front side passage 19, and theycorrespond to the second passage of the present invention.

In the radiator of the second embodiment, high-temperature flowingmedium entering the front side passage 19 through the inlet portincreases its flow speed due to a narrow flow area thereof to swiftlyflow to a top portion and a bottom portion of the inner space of theright tank 2, being mixed up with low-temperature flowing mediumexisting in the front side passage 19 in a short time. Then the flowingmedium flow to a left tank through all of not-shown tubes used for acore part at approximately uniform temperature.

On the other hand, the low-temperature flowing medium in the chambers31-37 is mixed up with the high-temperature, flowing medium flowingthrough the front side passage 19, via a clearance formed between tipportions of the first and second rib portions 18 and 30 and the wallportion formed by a not-shown tube plate. In this mix-up state, thesecond rib portions 30 obstruct the low-temperature flowing medium toflow in the longitudinal direction of the right tank 2, therebyaccelerating mix-up of the low-temperature flowing medium in thechambers 31-37 and the high-temperature flowing medium in the front sidepassage 19.

Therefore, the radiator of the second embodiment can provide thefollowing effects in addition to those of the first embodiment.

In the radiator of the second embodiment, the high-temperature flowingmedium can be preferentially guided into the narrow front side passage19 to accelerate its flow speed in the right tank 2. In addition, thesecond rib portions 30 can accelerate a speed of replacement, or mix-up,between the high-temperature flowing medium and the low-temperatureflowing medium in the right tank 2, thereby providing approximatelyuniform temperature distribution in the right tank 2.

Next, a third embodiment of the present invention will be described.

As shown in FIG. 9, in a radiator of the third embodiment, the heightsof a first rib portion 18 and first-rib-portion side portions of secondrib portions 30 are set to be lower than those of the second embodiment.The other parts are constructed similarly to those of the firstembodiment.

Therefore, the radiator of the third embodiment can provide thefollowing effect in addition to those of the second embodiment.

The first rib portion 18 and the portions of the second rib portions 30are formed lower, which can simplify a shaping die for a tank formed byusing resin mold, thereby saving a cost of the shaping die.

Next, a fourth embodiment of the present invention will be described.

As shown in FIG. 10 and FIG. 11, in a radiator of the fourth embodiment,a first rib portion 18 shown in the second embodiment is removed, andrib second rib portions 30 are provided similarly to those of the thirdembodiment. The other parts are constructed similarly to those of thefirst embodiment.

Therefore, the radiator of the fourth embodiment can provide thefollowing effect in addition to those of the second embodiment.

In the radiator of the fourth embodiment, high-temperature flowingmedium preferentially guided into a narrow front side passage 19 toaccelerate its flow speed in a right tank 2, further accelerating aspeed of replacement, or mix-up, between the high-temperature flowingmedium and the low-temperature flowing medium in the right tank 2,thereby providing approximately uniform temperature distribution in theright tank 2.

FIG. 12 shows the effects of the radiator of the first embodiment, andthe effects are similarly obtained in the second to fourth embodiments.

In a table of FIG. 12, an experiment result of the radiator 1 withoutthe first and second rib portions 13 and 30 is shown at a top part, ananalysis result of the radiator 1 without the first and second ribportions 13 and 30 is shown at a middle part, and an analysis result ofthe radiator 1 with the first rib portion 18, corresponding to the firstembodiment. Note that the right tank 2 is shown at the left side and theleft tank 3 is shown at the right side in FIG. 12. Therefore, theflowing medium flows from the left side to the right side in FIG. 12. Asthe temperature (Temp.) in the radiator 1 becomes higher, the color isshown darker in FIG. 12. Incidentally, “Ts” indicates the surfacetemperature of the radiator 1, and “Tf” indicates the temperature of thefollowing medium.

The experiment was carried out in such a way that at the beginning theradiator was cooled by being supplied with the low-temperature flowingmedium and then the high-temperature flowing medium was supplied to theright tank 2 with counting time. In order to obtain its higher accuracyof the analysis result, the analysis was performed, its data beingcompared with the experimental results.

After one second, the temperature of the right tank 2, shown as a widevertical bar at the left side in FIG. 12, with the first rib portion 18becomes approximately uniform at almost all portions of the right tank2, although the temperature of the right tank 2 without the first andsecond rib portions 18 and 30 becomes uneven in the right tank 2, wherethe temperatures of the top portion and the bottom portion of the righttank 2 are notably lower than that of its middle portion at one second.

This shows that the radiators of the embodiments are superior to theconventional radiator, in accelerating the temperature so that itbecomes uniform at the right tank 2.

While there have been particularly shown and described with reference topreferred embodiments thereof, it will be understood that variousmodifications may be made therein, and it is intended to cover in theappended claims all such modifications as fall within the true spiritand scope of the invention.

For example, as shown in FIG. 13, the flow accelerating means may employa U-letter shaped portion 40 that is formed to dent toward the inletport 13 to form a first passage between the inlet port 13 and a bottomwall of the U-letter shaped portion 40. A flow area therebetween isformed to be narrower than that of the inlet port 13. The U-lettershaped portion 40 corresponds to the first wall portion of the presentinvention.

The flow accelerating means may employ an L-letter shaped portion 41,partially dented in a height direction, which has a short height portion41 a and a long height portion 41 b so that the first passage and a partof the second passage are formed between the short height potion 41 aand the inlet port 13, and so that the rests of the second passages areformed between the short height potion 41 a and the wall portion withthe inlet port 13 and between the long height portion 41 b and the wallportion with the inlet port 13. The short height potion 41 a of theL-letter shaped portion 41 corresponds to the first wall portion of thepresent invention.

The heat exchanger is not limited to the radiator, and it may be acondenser or others.

A position of the inlet port 13, and configurations, dimensions, such asthicknesses and heights, and the numbers of the first rib portion 18 andthe second rib portion 30 may be set appropriately.

The flow accelerating means may be provided to the second tank inaddition to the first tank.

In the embodiments, the right tank 2 is the first tank and the left tank3 is the second tank, to which the first tank and the second tank arenot limited. The first tank may be one of right and left tanks or one ofupper and lower tanks as long as it has an inlet port.

The tanks, which are made of plastic material in the embodiments, may bemade of aluminum.

The first rib portion 18 and the second rib portion 30 may be made ofmetal material and is integrally formed with the tank by using insertmolding.

The entire contents of Japanese Patent Application No. 2007-265298 filedOct. 11, 2007 are incorporated herein by reference.

1. A heat exchanger, in which flowing medium flows, comprising: a firsttank that is provided with an inlet port; a second tank that is disposedapart from the first tank; a core part that has a plurality of tubes anda plurality of fins, the tubes having both end portions beingfluidically connected with the first tank and the second tank,respectively, and each of the fins being arranged between the adjacenttubes; and a flow accelerating means that is provided inside the firsttank so as to accelerate a flow speed of the flowing medium, whichenters an inner space of the first tank through the inlet port, in thefirst tank in a longitudinal direction of the first tank.
 2. The heatexchanger according to claim 1, wherein the flow accelerating means hasa first passage extending in the longitudinal direction and having aflow area narrower than a flow area of the inlet port.
 3. The heatexchanger according to claim 2, wherein the flow accelerating means hasa first wall portion extending in the longitudinal direction.
 4. Theheat exchanger according to claim 3, wherein the first wall portion is afirst rib portion formed in the inner space of the first tank so thatthe first rib portion divides the inner space of the first tank into thefirst passage and a second passage so that the flowing medium can beaccelerated to flow through the first passage and so that the flowingmedium in the second passage is not accelerated to flow therethrough,and wherein the flowing medium in the first passage and the flowingmedium in the second passage are capable of being replaced therebetweenthrough a clearance formed by the first rib portion.
 5. The heatexchanger according to claim 2, wherein the flow accelerating means isformed with the first tank as one unit made of plastic material.
 6. Theheat exchanger according to claim 2, wherein the first tank is anupstream side tank.
 7. The heat exchanger according to claim 1, whereinthe flow accelerating means has a first wall portion extending in thelongitudinal direction and having a flow area narrower than a flow areaof the inlet port.
 8. The heat exchanger according to claim 7, whereinthe first wall portion is a first rib portion formed in the inner spaceof the first tank so that the first rib portion divides the inner spaceof the first tank into the first passage and a second passage so thatthe flowing medium can be accelerated to flow through the first passageand so that the flowing medium in the second passage is not acceleratedto flow therethrough, and wherein the flowing medium in the firstpassage and the flowing medium in the second passage are capable ofbeing replaced therebetween through a clearance formed by the first ribportion.
 9. The heat exchanger according to claim 7, wherein the flowaccelerating means is formed with the first tank as one unit made ofplastic material.
 10. The heat exchanger according to claim 7, whereinthe first tank is an upstream side tank.
 11. The heat exchangeraccording to claim 1, wherein the flow accelerating means has a secondwall portion extending in a direction perpendicular to the longitudinaldirections to form a second passage where the flowing medium in thesecond passage is not accelerated to flow therethrough and is capable ofbeing replaced with the flowing medium in the first passage. 12 The heatexchanger according to claim 11, wherein the second wall portion is asecond rib portion for forming the second passage and for obstructingthe flowing medium entering through the inlet port from beingaccelerated to flow in the second passage.
 13. The heat exchangeraccording to claim 9, wherein at least one of the first wall portion andthe second wall portion is formed in such a way that a wall portion ofthe first tank is partially dented toward the inner space to form thefirst passage and a second passage where the flowing medium in thesecond passage is not accelerated to flow therethrough and is capable ofbeing replaced with the flowing medium in the first passage.
 14. Theheat exchanger according to claim 9, wherein the flow accelerating meansis formed with the first tank as one unit made of plastic material. 15.The heat exchanger according to claim 9, wherein the first tank is anupstream side tank.
 16. The heat exchanger according to claim 1, whereinthe flow accelerating means is formed with the first tank as one unitmade of plastic material.
 17. The heat exchanger according to claim 16,wherein the first tank is an upstream side tank.
 18. The heat exchangeraccording to claim 16, wherein the first tank is an upstream side tank.